Head and Tail
The head and tail commands show the beginning or end of files. They're essential for previewing files and monitoring logs.
head - View Beginning
head filename
By default, shows first 10 lines.
tail - View End
tail filename
By default, shows last 10 lines.
Specifying Number of Lines
head Options
head -n 5 file.txt # First 5 lines
head -5 file.txt # Same thing (shorthand)
head -n -5 file.txt # All BUT last 5 lines
tail Options
tail -n 5 file.txt # Last 5 lines
tail -5 file.txt # Same thing (shorthand)
tail -n +5 file.txt # Starting from line 5
Follow Mode (tail -f)
Watch a file for changes in real-time:
tail -f /var/log/syslog
This is invaluable for monitoring logs. Press Ctrl+C to stop.
Exercise: View First Lines
View the first 3 lines of a log file:
Common Options
| Command | Description |
|---|---|
head -n 20 | First 20 lines |
tail -n 20 | Last 20 lines |
tail -f | Follow file (live updates) |
tail -F | Follow, even if rotated |
head -c 100 | First 100 bytes |
tail -c 100 | Last 100 bytes |
Combining with Pipes
Get Lines from Middle
head -n 20 file.txt | tail -n 10 # Lines 11-20
Preview Multiple Files
head -n 5 *.txt
Monitor Multiple Logs
tail -f /var/log/*.log
Real-World Examples
Check Recent Log Entries
tail -n 50 /var/log/syslog
Monitor Log in Real-Time
tail -f /var/log/auth.log
Quick File Preview
head README.md
head -n 1 /etc/passwd # Just first line
Extract Specific Range
# Lines 100-110
head -n 110 file.txt | tail -n 10
Exercise: View Last Lines
View the last 2 lines of a config file:
Key Takeaways
headshows beginning,tailshows end- Default is 10 lines, use
-nto change tail -ffollows file changes in real-time- Essential for log monitoring
- Combine with pipes for precise line selection